Abstract:

A review of some unusual structural and electronic properties of several reduced molybdenum oxides with strong metal-metal bonds will be presented. These compounds have been prepared either by fused-salt-electrolysis employing Na2MoO4-MoO3 melts, or by direct solid-state reactions. Particular reference will be made to the observation of magnetic order in Sm4Mo18O32 and La5Mo4O16 crystals. Sm4Mo18O32 exhibits a metal to insulator transition below 270 K and ferromagnetic-like order below ~110 K. The electrical resistivity of this compound did not show the expected magnetic field dependence implying that the two transitions originate from different bands. Results of these studies will also be compared to our earlier investigations on the Ln4Mo18O32 (Ln = Y, Nd, Gd-Ho) all of which displayed strong metal-insulator transitions. Crystals of La5Mo4O16 show significant anisotropy in their magnetization with a meta-magnet like transition around 180K. The effect of 3d transition metal ion substitution effects on the meta-magnetic transition of La5Mo4O16 will also be presented.